Petrographical, geochemi̇cal and petrological investigation of the mavri̇yas (Çaykara-Trabzon) granitoid and surrounding rocks

In this study which focus on petrographic, geochemical and petrological characteristics of Mavriyas Granitoid and surrounding rocks in Çaykara (Trabzon) region, aims to reveal the origin of Mavriyas Granitoid by considering its petrogenetic process. The basement of the study area is Late Cretaceous volcanic rocks which are represented by basalt, andesite, dacit and their pyroclasts. This unit is cut by Eocene aged Uzuntarla Granitoid and it is observed that the Late Cretaceous Mavriyas Granitoid which constitutes the subject of the study is intercalated into the unit. Alluvium unconformably overlies the Late Cretaceous volcanic rocks, Late Cretaceous Mavriyas Granitoid and Eocene aged Uzuntarla Granitoid. The granitoid-bearing rocks are coarse-to-medium dense and contain plagioclase, quartz, orthoclase, hornblende and opaque minerals. Mavriyas Granitoid is elliptical and covers an area about 6 km2. It consists of granite, monzogranite, granodiorite, alkali feldspar and granitic rocks and contains mafic microgranular enclaves (MMA) in the quartz monzodiorite composition. Simultaneously, rocks forming granitoids also showed poikilitic texture, imbricate texture, plagioclase and K-feldspar phenocrysts in mafic microgranular enclaves. The rocks forming the Mavriyas Granitoid are generally I type, calc-alkaline with high K content and have high SiO2 contents (62.72-77.9 wt%). The rock samples forming the granitoid indicate the transition from metal to perlite, showing the characteristic of volcanic arc granitoids. Major and trace element changes demonstrate that plagioclase, hornblende, apatite and Fe-Ti oxide fractionation play significant role in the development of granitoid. Considering the petrological characteristics of Mavriyas Granitoid, fractional crystallization, mixture of magma and assimilation and partial melting play a role in the development of granitoid. Geochemical data indicate that the lithospheric mantle components play an important role besides the partial melting of the granitoid subcontinental crustal rocks (amphibolitic).